The most common way of extending the freshness of food materials such as fruits and vegetables has been to subject said materials to heat such as blanching or in extreme cases sterilizing. The problem with heat treatment is that, the requisite amount of heat required for destroying the microorganism which cause deterioration of the food materials often times causes undesirable changes within the food material. For instance, in case of fruits and vegetables changes such a denaturaton of proteins; degradation of strarches; destruction of vitamins, flavor and color pigments will generally occur. The most severe degradation generally occurs in the canning of these food product. Canning exposes the product to drastic heat treatment which adversely affects the color, flavor and texture of the finished product.
To avoid heat treatment, attempts have been made to preserve fruits and vegetables by treatment with acids or alkalies. For instance, U.S. Pat. No. 1,098,006 by Allen teaches preserving food substances such as fruit and vegetable pulp by treating with hydrochloric acid followed by neutralizing with sodium bicarbonate prior to use. It is believed that processing in an acidic environment generally shortens the time the food material is thermally processed which in turn decreases product degradation due to heat created within the container. This treatment, however, still affects particularly, the flavor and color of the product. U.S. Pat. No. 3,328,178 by Gordon teaches treating the food material with an acid and restoring the food product to its original pH by neutralization prior to thermal processing. U.S. Pat. No. 2,214,419 by Jones treats the food material with an alkali followed by neutralization with an acid prior to thermal processing. Pretreatment is believed to be less detrimental since the conditions within the containers are neither acidic or alkaline. These references, however, still involve thermal processing which has negative effects on the product.
Other references of general interest as follows.
U.S. Pat. No. 3,814,820 by Busta et al discloses treating fruits and vegetables by washing in an aqueous detergent solution of a phosphate at a pH preferably from 8 to 9, followed by contacting the product with an aqueous sanitizing agent such as a hypochlorite and treating the product with a discoloration inhibitor such as ascorbic acid at a pH preferably from 5.8 to 6.5.
U.S. Pat. No. 2,417,932 by Kalmar discloses treatment of fruits and vegetables, particularly potatoes with an aqueous solution of a hypochlorite, followed by treatment with an aqueous solution of a reducing agent such as a bisulfite or a phosphite.
U.S. Pat. No. 1,242,728 by Schneible discloses pasteurizing green vegetables such as asparagus by immersion in an alkali solution.
U.S. Pat. No. 176,754 by Mefford et al discloses preserving fruits by subjecting the products to an atmosphere of sulphorous acid followed by drying.
None of the above references disclose the treatment of fruits and vegetable with acid shock followed by alkali shock.
It is, therefore, an object of the present invention to reduce the total population of microorganisms on the surface of fruits and vegetables without the use of heat treatment.
Another object of the present invention is to reduce the natural pathogens of food microflora.
Still a further object of the present invention is to reduce the microbial load thereby extending the shelf life of foods products at refrigeration temperatures.